59 Oz holding torque?

[Chalkbot]

Hi everyone, my first post on these forums.

I recently came into possession of about 50 stepper motors from a garage sale. I have never done anything with steppers, but now that I have a bunch of them I thought I might try making a CNC machine. My only concern is these motors may not be strong enough for the job. The spec sheet on them says they are rated at 59 oz.

Forgive my ignorance, but can I compensate for the lesser torque of the motor by using rods that are more tightly threaded? This makes sense in my head, in that the end result would be that my machine was slower, but still have enough power to mill stuff.

Is it as simple as that, or are there more variables involved? Any wisdom or experience you can offer me would be greatly appreciated.

I also have a TON of extra steppers if people on these boards are interested.

[jeffs555]

This page has a list of various acme screws. http://www.nookindustries.com/acme/AcmeAvailability.cfm
It has a column showing "torque to raise 1 lb". If multiply that column by the number of lbs force you need it will give you the torque required in in-lbs. Divide that by 16 to get in-oz. You do need to be aware that starting torque will probably be less than the 59oz holding torque. Also, for all steppers, torque drops as rpms increase. The only way to know is to look at the torque curves for your motor.

[Chalkbot]

Thanks Jeffs555!

I looked at the chart you linked and what you said makes sense to me, but there is just one question in my mind. How do I know how many pounds of force I need?

Does it vary based on what I'm cutting and/or how much my machine weighs? I feel so stupid asking a question like this as I'm sure it's comparable to my mom asking me non-sensical questions about her computer's "megahertz".

Is there a standard amount of force I would need to cut wood, aluminum, steel, etc., and where might I get these figures?